Behavioral assessments of severe behavior disorders of children with developmental disabilities have revealed that behavioral problems are often maintained by their functional outcomes (or reinforcers). For example, children may gain caregiver attention or escape from instructional demands via their problem behavior. Behavioral interventions built upon this framework comprise the current standard of psychological care. These interventions typically involve teaching or otherwise promoting appropriate, alternative behaviors that produce identical or similar reinforcers as the problem behavior, thereby obviating the need for the child to engage in the aberrant behavior. Numerous studies have validated the effectiveness of these interventions under initial conditions, but others have revealed that their therapeutic effects sometimes diminish as the ratio of responses to reinforcers is increased (or "thinned") to make the interventions practical in natural environments (e.g., classrooms). Principles from the field of behavioral economics can help to determine the conditions under which behavioral interventions can be expected to maintain their effects across changes in reinforcement delivery schedules. Specifically, the behavioral economic concepts of substitutability and demand elasticity have revealed that demand for a commodity (in behavioral terms, choosing one reinforcer over concurrently available reinforcers) is a joint function of its cost (the number of responses required to produce that reinforcer) and the degree to which concurrently available commodities are more substitutable. The implication of these findings for behavioral interventions is that problem behaviors may be more likely to reemerge as schedule thinning progresses when the available alternatives are functionally similar. These principles thus suggest, paradoxically, that the provision of the same or similar outcome contingent upon an alternative behavior may not always be the best therapeutic option in treating behavior disorders. In the current proposal, two studies will extend out pilot data demonstrating how behavioral economic principles can be brought to bear on the orderly choice responding of individuals with developmental disabilities. Two subsequent experiments will employ these same principles to determine the conditions under which behavioral interventions based on providing reinforcers that are functional dissimilar to those historically produced by behavior problems may be expected to have superior clinical effects than interventions based on providing functionally similar outcomes. [unreadable] [unreadable]